View Larger Image A view inside the firing chamber of the John Thies’ Manabigama kiln, which was designed with education in mind.

March 24, 2007

Manabigama: 24 Cubic Feet of Kiln Space

by John Thies | Read Comments (3)

For more than thirty years now, I have been building, firing and maintaining various large wood kilns. Almost all of them have been a design taken directly from the chamber kilns used historically around the world. My present kiln is fired seven times a year for my personal work and also for group workshops. The kiln is a 300-cubic-foot crossdraft, with three chambers in the traditional noborigama style. Two of the chambers are used for glazework and one is used for salt glazing.

I started using this kiln nine years ago for teaching group workshop firings. I schedule three a year, which is all I can manage given the labor and time involved. Each year, the groups enjoy the experience and the work that comes from it, but many ask for additional space in my kiln at other times during the year, which is not possible given my production schedule.

With new ideas in mind, I set out to build a very versatile and efficient wood-firing kiln that could be used by students who had interest in a complete hands-on experience, from the preparation, loading, firing and unloading to the final clean-up phase. I didn’t want to interfere with the successful larger firings, in which students can get a large volume of wood-fired pots without the in-depth hands-on experience. The new kiln would allow me to cut down on the extensive labor, fuel and overhead costs of my larger kiln.

I named the new kiln “Manabigama” at the suggestion of my friend Phil Berneburg, former technical editor for CM. In Japanese, mana means educational or learning, bi means a thing of beauty, and gama means kiln. The Manabigama is a traditional design with a few simple modifications. I see it as a cross between an anagama and a groundhog-style kiln. Basically, it is a crossdraft tube built into the side of a hill.

The overall interior dimensions are 24 inches in width, 7 feet in depth, 40 inches in height. Its firebox is in the front, incorporated into the inside with a grate system, and extra air intakes are built into the front and sides. This is done to provide more secondary air intake to help burn green or wet fuel. The firebox is plenty adequate being 2 feet wide, 2 feet deep and 30 inches high from the floor to ware level. The chimney has inside dimensions of 9 inches deep by 18 inches wide and is 12 feet high. The shape is a long rectangle with two straight, 18-inch-tall side walls and a catenary arch built on top. This creates ample headroom for ease of loading, as well as extra height for stacking and tall pieces.

There is approximately 24 cubic feet of ware space, more than enough for teaching purposes. The kiln door is in front, only halfway down, and is bricked up including the stoke hole. It can be loaded in two to
three hours, fires evenly to Cone 10–12 in eight hours tops, or if you choose, you can fire two to three days depending on how much ash buildup you like. The consumption of fuel is also minimal—less than half a cord of wood.

All in all, the Manabigama is a very simple design to build. It is capable of yielding wonderful ash-glazed pieces with a minimum of labor, fuel and overhead costs. And it is a fantastic wood-fired kiln for teaching without the tremendous strain of a large three-chambered kiln.